Gyroscopes are often used for sensing a rotation or an attitude of an object along one or more axes of rotation. For example, gyroscopes have long been used in naval vessels, aircraft, and spacecraft to identify rotation of the craft and for use in stability control systems. More recently, gyroscopes have been incorporated in micro-electromechanical (MEMS) devices. While classical gyroscopes rotate around an axis, MEMS gyroscopes typically include vibrating elements that are formed using photolithographic processes in an integrated circuit that is suitable for mounting to a printed circuit board or with other electronic components. As the MEMS device rotates around an axis, the plane of oscillation for the vibrating element tends to remain constant, and a modulated electrical signal from the MEMS sensor corresponds to the attitude of the support for the MEMS device around the axis. Some MEMS devices include multiple vibrating gyroscope elements that enable sensing of rotation along multiple axes in a three-dimensional space.
State of the art MEMS gyroscopes are used in a wide range of devices including, but not limited to, smartphones, tablets, and other portable electronic devices. For example, many portable devices include a display screen that displays text and graphics in either a portrait or a landscape orientation. A MEMS gyroscope in the mobile electronic device generates signals corresponding to the rotation of the device between the landscape and portrait orientations, and a microprocessor in the mobile electronic device adjusts the graphical display based on the signals from the gyroscope. Additional uses for MEMS gyroscopes in mobile devices include, but are not limited to, user input and inertial navigation applications.
While MEMS gyroscopes have become popular in compact electronic devices, the structure and operating conditions for existing MEMS gyroscopes introduce errors into the signals that are generated in the gyroscope. For example, the different manufacturing tolerances and fluctuating operating temperatures of MEMS gyroscope generate a quadrature signal error in the output of the signal from the vibrating sensing element in the gyroscope. A demodulation phase error is introduced due to the delays in the mechanical sensing element and electronic components that receive the modulated analog signals from the gyroscopic sensor and generate demodulated digital signals that are suitable for processing with digital microprocessors. Existing solutions for mitigating the offset drift errors include complex closed-loop feedback circuits that increase the cost, complexity, and electrical power consumption of the gyroscopic sensor system. Thus, improvements to circuits that process signals generated in vibrational gyroscopic sensors with reduced offset drift error would be beneficial.